Display screen or a portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or a portion thereof with a graphical user interface showing our new design.

The lighter-toned shaded portions in the drawing illustrate portions of the display screen or portion thereof with a graphical user interface that forms no part of the claimed design. The outermost broken lines in the drawing show a display screen or portion thereof, and form no part of the claimed design. The remaining broken lines in the drawing show portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or a portion thereof with a graphical user interface, as shown and described. 